Document 1
ELECTROCHEMISTRY:
GALVANIC CELLS
Zinc Anode
Copper Cathode
OXIDATION
REDUCTION
Cl -
Zn
e-
Salt Bridge
K
KCl Membrane
+
Cu
e-
Potentiometer
Reducing
Agent
Oxidizing
Agent
Source
Galvanic Cell Experiment. 3d rendering. (n.d.).
https://www.shutterstock.com/imageillustration/galvanic-cell-experiment-3d-rendering1732394242
HOW IT WORKS?
01
Oxidation: the reducing agent
oxidized releasing an electron.
What is a galvanic cell?
is
Zinc oxidizes and dissolves into the solution as a zinc
cation, which traverses the bridge and enters the
adjacent beaker, or a half-cell. An electron is released on
the process and flows away from the anode.
02
Reduction: the oxidizing agent
reduced by taking an electron.
is
Zinc sulfate is made when the zinc cation replaces the
copper cation. The copper cation combined with the
sulfate anion to make the copper sulfate solution before
it was dissolved. The electron released in the first halfcell goes to the cathode, where it reduces the copper
cation to a copper atom. The sulfate anion left behind
crosses the bridge and enters the first half-cell through
the salt bridge. It then interacts with the oxidized zinc
cations to form zinc sulfate.
03
Also called a voltaic cell, it is an electrochemical
cell that converts the chemical energy of
spontaneous redox (reduction-oxidation)
reactions into electrical energy.
bridge maintains electroneutrality
04 Salt
(no charge buildup) throughout the cell.
KNO3-rich gel fills a salt bridge. Porous glass disks at the
bridge's ends distribute ions but prevent solution mixing. The
galvanic cell moves K+ from the bridge to the cathode
compartment and a little quantity of Cl- from the cathode to
the bridge. Ion migration prevents cathode charge
accumulation via electron flow. The migration of ions out of
the bridge is greater than the migration of ions into the
bridge because the salt concentration in the bridge is much
higher than the concentration
in the half-cells.
A redox reaction involves
transfer of electrons from one
species to another. A species
is said to be oxidized when it
These reagents should be physically
separated.
The two cannot be in contact, or electrons would flow
directly from the reducing agent to the oxidizing agent.
The electrons are forced to flow from one half-cell to
another via an external circuit.
losses electrons, while reduced
when it gains electrons.
REFERENCES:
[1] Harris, D. C. (2007). Quantitative Chemical Analysis (7th ed., pp.
270-277). Craig Bleyer.
[2] Peshin, A. (2023, January 4). How Does A Galvanic Cell Work?
Science
ABC.
Retrieved
February
12,
2023,
from
https://www.scienceabc.com/innovation/galvanic-cell-work.html
Document 2
GALVANIC CELLS:
BATTERIES AND FUEL CELLS
Batteries and fuel cells are galvanic cells that consume their reactants.
Energy storage and conversion is one of the oldest and most essential uses of electrochemistry.
BATTERIES
Similar to how a galvanic cell transforms chemical
energy to work, an electrolytic cell converts electrical
work into chemical energy. Batteries are devices that
carry
out
these
conversions.
The
chemical
components of standard batteries are contained
within the device itself.
Lead-acid storage cell
The main difference between batteries and the
galvanic cells is that commercial batteries use solids
or pastes instead of solutions as reactants in order to
maximize electricity out of each unit of mass. Using
highly concentrated or solid reactants has another
benefit: as the battery is discharged, the
concentrations of the reactants and the products don't
change much. As a result, the output voltage stays
very stable during the discharge process. This is
different from the Zn/Cu cell, whose output goes down
in a logarithmic way as the
reaction goes on.
How are they different?
A battery contains all the reactants needed to
produce electricity. In contrast, a fuel cell
requires a constant external supply of one or
more reactants to generate electricity.
Modern hydrogen-oxygen
fuel cell
FUEL CELLS
A fuel cell is a galvanic cell that requires a
continual external supply of reactants due to
the continuous removal of reaction products.
Unlike a battery, a fuel cell extracts electrical
energy directly from a chemical process, as
opposed to storing chemical or electrical
energy. Most practical fuel cells generate H+ at
the anode (from H2 or a hydrocarbon), and
oxygen from the air is converted to H2O at the
cathode. Commonly used electrolytes are
NaOH solution, phosphoric acid, or solid oxides.
In theory, this should be a more efficient
process than burning gasoline to drive an
internal combustion engine that powers a
generator, which is often less than 40% efficient.
In practice, however, the efficiency of a fuel cell
is normally between 40% and 60%. Sadly,
substantial cost and dependability issues have
prevented the widespread implementation of
fuel cells. In practice, its usage has been limited
to situations where bulk is a considerable
economic consideration.
A major limitation of any oxygen-consuming fuel cell is the slow rate of the
reduction of this element at a cathode. The best cathode surfaces are
usually made of platinum, which is a major cost factor in fuel cell design.
Despite having the highest energy-to-mass ratio of any fuel, hydrogen
cannot be compressed to a liquid at room temperature. If it is kept as a
gas, the extremely high pressures necessitate large storage vessels, limiting
its effective energy density significantly.
REFERENCE:
[1] Libretexts. (2022, September 19). 20.7: Batteries and Fuel Cells. Chemistry LibreTexts. Retrieved February 24,
2023, from https://chem.libretexts.org/Bookshelves/General_Chemistry/Map:_Chemistry__The_Central_Science_(Brown_et_al.)/20:_Electrochemistry/20.07:_Batteries_and_Fuel_Cells
Document 3
FUEL CELLS
Porous Anode
Porous Cathode
Source
Hydrogen fuel cells, explained: Hydrogen fuel cells:
how do they work? (2020, October 15). Airbus.
https://www.airbus.com/en/newsroom/news/2020
-10-hydrogen-fuel-cells-explained
Polymer Electrolyte
Membrane (PEM)
HOW IT WORKS?
01
The hydrogen atoms enter at the
anode.
Here, hydrogen atoms react with a catalyst (i.e.
platinum) and split into electrons and protons. Oxygen
from the ambient air enters on the other side through the
cathode.
02
03
The atoms are stripped
electrons in the anode.
of
their
PEM allows the positively charged
protons to pass through to the
cathode, but not the negatively
charged electrons.
The negatively charged electrons must flow around the
membrane through an external circuit. This flow of
electrons forms an electrical current. The negatively
charged electrons must flow around the membrane
through an external circuit. This flow ofelectrons forms an
electrical current.
04
In the cathode, the protons and
oxygen then combine to produce
water and even heat.
Fuel Cell Components
PEM
PEM is a thin, solid organic polymer with the
consistency of plastic wrap and a thickness of 2
to 7 sheets of paper. This membrane acts as an
electrolyte, which is a material that carries
protons but not electrons. As a result, the solution
conducts electricity. To allow particles to pass
through, this membrane must be kept moist.
Anode
Platinum particles evenly supported on carbon
form the anode. Platinum speeds up oxidation.
Hydrogen passes through the porous anode.
Cathode
Platinum particles evenly supported on carbon
form the cathode. Platinum speeds up reduction.
Oxygen passes through the porous cathode.
Flow Plates
Flow plates have several purposes:
1. They supply hydrogen and oxygen to
electrodes.
2. They remove heat and water from fuel cells.
3. Electrons go from the anode to the electrical
circuit and back to the cathode.
Document 3
FUEL CELLS
Different Types of Fuel Cells
Alkaline Fuel Cells (AFC)
AFC's use alkaline electrolytes like potassium
hydroxide. Generally, a solution of potassium
hydroxide in water is used as the electrolyte. The
cell operates at 150-200 degrees Celsius, and
can generate anywhere from 300 W to 5 MW.
Molten Carbonate Fuel Cells (MCFC)
MCFC's use molten carbonate salts as their
electrolyte. This fuel cell has a high electrical
efficiency of 60 %. These cells operate at about
600 degrees Celsius. The generated power
varies, and some units have been built with
outputs as high as 100 MW. Because of the high
temperatures, these cells are not generally used
in the home.
Zinc Air Fuel Cells (ZAFC)
In this type of fuel cell, there is a gas diffusion
electrode, a zinc anode separated by electrolyte
and a mechanical separator. Oxygen is reduced
to hydroxide, which combines with oxidized zinc,
generating electrons in the process.
Phosphoric Acid Fuel Cells (PAFC)
This fuel cell's anode and cathode are made with
specks of platinum on a carbon and silicon
carbide matrix that supports the phosphoric acid
electrolyte. PAFC's are commonly used in large
commercial vehicles i.e. buses and were the first
fuel cells to be commercialized.
Proton Exchange Membrane Fuel Cells
(PEMFC)
This fuel cell uses a polymeric membrane as the
electrolyte along with platinum-activated,
carbon-based electrodes. PEMFC's can function
at relatively low temperatures and are therefore
commonly used in scenarios requiring short
start-up times, including transport and portable
applications.
Direct Methanol Fuel Cells (DMFC)
This fuel cell is similar to the Proton Exchange
Membrane Fuel Cell; however, instead
of using gaseous hydrogen as the fuel, liquid
methanol is used.
Solid Oxide Fuel Cells (SOFC)
SOFC's can operate from ~ 550 °C to 1000 °C.
SOFC's are able to do so because they use a
solid ceramic electrolyte between their
electrodes. Like MCFC's, SOFC's can also perform
at an efficiency of around 60 %. These fuel cells
are often used for generating heat and electricity
in industry and for providing auxiliary power in
motor vehicles.
Document 3
FUEL CELLS
Pros
Cons
Renewable and Readily Available
Hydrogen Extraction
Hydrogen, the most common element in the
Universe, is a renewable and plentiful energy
source ideal for zero-carbon combined heat and
power sources.
Hydrogen, the most plentiful element in the
Universe, must be electrolyzed from water or
separated from carbon fossil fuels. Both
processes demand lots of energy. This expensive
energy is more than hydrogen's. Without CCS,
this extraction usually needs fossil fuels, which
reduces hydrogen's "greenness".
Hydrogen is a Clean and Flexible
Energy Source to support ZeroCarbon Energy Strategies
Hydrogen fuel cells produce heat and water,
making them a clean energy source.
More Powerful and Energy Efficient
than Fossil Fuels
High-pressure gaseous and liquid hydrogen
have 3 times the gravimetric energy density
(120MJ/kg) of diesel and LNG and equivalent
volumetric energy density to natural gas.
Highly Efficient when Compared to
Other Energy Sources
Hydrogen fuel cells generate energy with 65%
efficiency compared to 33-35% for combustionbased power plants. Hydrogen fuel cells in
vehicles use 40-60% of fuel energy and reduce
fuel usage by 50%.
Almost Zero Emissions
Hydrogen fuel cells emit no greenhouse gases,
improving air quality and lowering pollution.
Reduces Carbon Footprints
Hydrogen fuel cells emit nearly no greenhouse
gases and leave no carbon impact.
Fast Charging Times
Hydrogen fuel cells recharge in five minutes,
while electric vehicles take 30–60 minutes.
No Noise and Visual Pollution
Hydrogen-powered cars are quieter. Hydrogen
fuel cells are less visually polluting than wind and
biofuel power facilities, which require more area.
Investment is Required
To develop and mature the technology, political
will is needed to invest time and money. Simply
put, developing ubiquitous and sustainable
hydrogen energy requires cost-effectively
building the "supply and demand" chain.
Cost of Raw Materials
Fuel cells and some water electrolyzers use
catalysts like platinum and iridium, which raises
their initial cost. Hydrogen fuel cell technology is
expensive. Hydrogen fuel cells must be
affordable for everyone.
Regulatory Issues
Commercial ventures often struggle to make
financial investment decisions without defined
legal frameworks for cost and revenue analysis
(FID).
Hydrogen Storage
This power supply infrastructure exists due to
decades of fossil fuel use. For long-range
applications like HGVs and delivery trucks, startto-end refuelling may be used, but large-scale
adoption of hydrogen fuel cell technology for
automotive applications will require new
refuelling infrastructure.
Highly Flammable
Hydrogen is a highly flammable fuel source,
which brings understandable safety concerns.
Hydrogen gas burns in air at concentrations
ranging from 4 to 75%.
REFERENCES:
[1] Libretexts. (2020, August 16). Case Study: Fuel Cells. LibreTexts Chemistry. Retrieved February 12, 2023, from
https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Electrochemistry/Exemplars/Case_Study%3A_Fuel_Cells
[2] Fuel Cell Animation (Text Version). (n.d.). Energy.gov. https://www.energy.gov/eere/fuelcells/fuel-cell-animation-text-version
[3] What are the Pros and Cons of Hydrogen Fuel Cells? (n.d.). https://www.twi-global.com/technical-knowledge/faqs/what-are-the-pros-and-cons-of-hydrogen-fuel-cells